/** @license
 * MIT License
 *
 * Copyright (c) 2018
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
import { createSelector } from 'reselect'
import { SHOW_ALL, SHOW_COMPLETED, SHOW_ACTIVE } from '../constants/TodoFilters'

const getVisibilityFilter = state => state.visibilityFilter
const getTodos = state => state.todos

export const getVisibleTodos = createSelector(
  [getVisibilityFilter, getTodos],
  (visibilityFilter, todos) => {
    switch (visibilityFilter) {
      case SHOW_ALL:
        return todos
      case SHOW_COMPLETED:
        return todos.filter(t => t.completed)
      case SHOW_ACTIVE:
        return todos.filter(t => !t.completed)
      default:
        throw new Error('Unknown filter: ' + visibilityFilter)
    }
  }
)

export const getCompletedTodoCount = createSelector(
  [getTodos],
  todos => (
    todos.reduce((count, todo) =>
      todo.completed ? count + 1 : count,
      0
    )
  )
)
